Players are the heart of D&D. Their special role is to interact with the DM, that may rightly be called the head of the game, and together bring to life the AD&D Spirit. The Spirit of the game is imbued within it's pages and play by the founder himself, but synergy of player and DM is what brings the magic to life.
In an age when core books include all there is to the game and game master guides are but a footnote of advice to GMs on how to run a game, this sets AD&D apart. Nowadays it is assumed that the players will know as much or more as the DM about the game and what they may be facing. It is simply assumed that the players will have all the monster manuals, the DM's guide and every other book in print and read it assiduously. They know the monsters you are going to throw at them, what magic items they might find and how to best handle poisons and traps that they may face.
Though modern gamers often laud this informational democracy as a good thing, as an advancement of fairness, in all reality this was never how the game was intended to be played. No it goes against the basic premise of the game: that players are adventurers heading out into the unknown. The players only need to know so much about the game. Why? Well, the foreword answers that very question, "this bit of the 'unknown' outside of the players' normal reach will make the game much more interesting and challenging."
And there you have it. What have we lost with the advent of gaming democracy? The players is already special, is the heart of the game, without which nothing happens at the table. He brings the magic alive as much as the DM does--perhaps even more because there are more of them. But as the game was createad there were definite roles at the table. Not the classes we play, but the roles of player and DM and there was a clear line of demarcation between them. The players were not to read the Dungeon Masters Guide, nor the Monster Manual--not if they wanted the game to be more "exciting and enjoyable." The Players Handbook was theirs, created especially for them. The structure of the book is the same as the Dungeon Masters Guide, so that they know each important element o the game, just not all the details. Only those salient to their role as players.
So the next time they come across that magic item, or trap or creature, there awaits them a sense of wonder, a thrill of fear and the very essence of adventure.